Mention milligram in the guides (#4570)
Mention milligram in the guides (#4570)

* Mention Milligram in guides

* Remove potentially-confusing acronym

0x00evil/phoenix,phoenixframework/phoenix,rafbgarcia/phoenix,0x00evil/phoenix,rafbgarcia/phoenix,phoenixframework/phoenix,optikfluffel/phoenix,nshafer/phoenix,0x00evil/phoenix,optikfluffel/phoenix,nshafer/phoenix,nshafer/phoenix,rafbgarcia/phoenix,optikfluffel/phoenix,phoenixframework/phoenix